What are the landmarks of Denver? The D&F Tower? Red Rocks Amphitheatre? Or maybe the giant airplane  that graces Constellation Ice Cream, which developer Paul Tamburello opened in Eastbridge Town Center at the end of March, an addition to the cityscape that’s a fitting followup to the giant milk can outside Tamburello’s Little Man Ice Cream?

May is National Historic Preservation Month, and to mark the occasion, Historic Denver has launched its third annual photo contest with the theme "Landmarks of Today and Tomorrow." The pictures can be of buildings that have been designated officially as Denver landmarks (such as Cableland, which became the latest, and youngest, city landmark on April 29), or simply a structure that seems to define Denver for you.

Historic Denver executive director Annie Levinsky points out that a winning photo in last year's contest, which had the theme "What Makes Denver Denver?," was of a car club meeting under the I-70 viaduct. "What makes a place meaningful depends on who's looking at them, using them," she points out. "Most people don't think of viaducts as landmarks."

Historic Denver staffers have their own nominees for meaningful places that one day could rate landmark designation. For example, Denver International Airport, "particularly the original structure," Levinsky says, adding that a lot of people are already talking about the Clyfford Still Museum, as well as the Michael Graves addition to the Denver Public Library (the original structure by Burnham Hoyt has already been recognized).

The Denver Coliseum "has some fans in this office, but its future is uncertain," she notes. Sadly, the future is all too certain for the Rio Grande grain elevators at 123 Santa Fe Drive; the owner applied for a demolition permit in March, and when no one filed to have them designated historic, the permit was issued.

The Bonnie Brae Tavern also just received a certificate of non-historic designation, though the family that's run the place for over eight decades say they have no plans to sell (much less demolish) it right now. Tom's Diner, a diner in a classic Googie structure on East Colfax Avenue, has "already been identified as architecturally signifiant," Levinsky notes; it's definitely on the block.

What do you consider a Denver landmark? Historic Denver wants to see it. “Submissions give all of us a deeper appreciation for our city’s architecture and the ways that we, as a community, interact with historic places and neighborhoods," according to the contest rules. "From everyday cell phone camera users to professional photographers, we welcome a wide range of beautiful imagery that captures Denver’s magic. Along with a prize package, winners will be highlighted on our website, social media channels and with a spread in Historic Denver News.”

Send your visual nominations by May 31 to [email protected]; find out more at historicdenver.org.

The City of Denver, too, is getting in on the act, with the #ThisPlaceMattersDenver program that includes a weeklong exhibit on Denver's preservation program, which opens Monday, May 6, at the Webb Municipal Building, 201 West Colfax Avenue, where it will run through Friday, May 10, during business hours. At 1 p.m. Wednesday, May 8, a lunchtime lecture titled "I Saw the Sign: Denver’s Signage and Preservation" will drill down on the city's program.

And through the month, you can share photos of landmarks, official or not, with the city's hashtag.